William Paul Troost-Ekong MFR MON (born 1 September 1993) is a professional footballer who plays as a centre-back for Qatar Stars League club Al-Ahli. Born in the Netherlands, he played for the Nigeria national team, earning more than 80 caps and serving as captain.

Troost-Ekong attended secondary school at Hockerill Anglo-European College in Bishop's Stortford, in England. He played football at youth level in England for Fulham and Tottenham Hotspur, Troost-Ekong began his senior career in the Netherlands with FC Groningen and FC Dordrecht.

After being linked abroad with transfers to Celtic among others, he signed for Belgian club KAA Gent in July 2015 and was immediately loaned out to Norwegian club FK Haugesund.

In July 2017, Troost-Ekong signed for Turkish Süper Lig club Bursaspor.

On 17 August 2018, Troost-Ekong joined Italian Serie A club Udinese. In his debut season in the Serie A, he made 35 league appearances and was booked four times, helping Udinese to 12th position. The next season, Udinese finished 13th, albeit with two more points. Despite the team's relatively lacklustre league campaigns, Troost-Ekong started (and played for the full 90 minutes) in memorable victories against AC Milan and Juventus in his two seasons at Le Zebrette.

On 29 September 2020, Troost-Ekong signed for EFL Championship side Watford on a five-year contract deal. He scored his first goal for the club in a 3–2 win over Coventry City on 7 November 2020.

On 24 January 2023, Troost-Ekong signed for Serie A club Salernitana on a loan with the option to buy at the end of the season.

On 4 July 2023, he joined Super League Greece club PAOK on a permanent deal for a free transfer.